One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,7)(4,6)(5,8)(11,17)(12,20)(14,22)(16,23)(18,24)(19,21)(25,26,28,31,29,32,35,38)(27,30,34,37,33,36,39,40)(1,3)(2,5)(4,8)(6,7)(9,10,13,15)(11,18,19,14)(12,16,20,23)(17,24,21,22)(25,27)(26,30)(28,34)(29,33)(31,37)(32,36)(35,39)(38,40)(3,8)(5,7)(9,11,13,19)(10,14,15,18)(12,21,20,17)(16,24,23,22)(2,6)(5,7)(10,15)(14,18)(16,23)(22,24)(27,33)(30,36)(34,39)(37,40) involution — undirectedA Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.